© 2000 by London Mathematical Society
© The London Mathematical Society
Definiteness of the Peano Kernel Associated with the Polyharmonic Mean Value Property
Department of Mathematics, Gerhard-Mercator-University Duisburg, 47048 Duisburg, Germany
Institute of Mathematics, Bulgarian Academy of Sciences 8 Acad. G Bontchev Str., 1113 Sofia, Bulgaria
Received 10 July 1998.
The definiteness of the Peano kernel is proved for a functional associated with the mean-value property of Picone and Bramble and Payne for polyharmonic functions in the ball. An important corollary of this is that if a function f satisfying (1)p
pf>0 vanishes on p concentric spheres centered at 0, then f(0)>0. This generalizes a well-known property of subharmonic functions (which arise in the special case p = 1).